351 cleveland fuel economy

Submitted: Friday, Jun 06, 2008 at 05:50
ThreadID: 58434 Views:18896 Replies:10 FollowUps:8
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I know that the 351 LPG carburettor dinosaur motor in my 1981 F100 is not going to get particularly good economy. However I am starting to draw the line at 3km/litre. Does anyone out there have any tips on fuel economy/performance upgrades for this motor?
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Reply By: Member - AJB (VIC) - Friday, Jun 06, 2008 at 06:00

Friday, Jun 06, 2008 at 06:00
Big engine, old deign, big vehicle, LPG conversion, poor aerodynamics makes it hard to achieve good fuel econmy. You have allready gone down the LPG route so think how much worse it would be if using petrol only. There are plenty of performance upgrades for these motors depending on its condition but they could be costly and wont improve economy that much. My tip would be drive it less and dont hammer tho go pedal.
AnswerID: 308043

Follow Up By: troopyman - Friday, Jun 06, 2008 at 06:06

Friday, Jun 06, 2008 at 06:06
Its a 351 , of course you hit the juice pedal . That would be like taking elle out and not juicing her up .
FollowupID: 573862

Reply By: 351c - Friday, Jun 06, 2008 at 06:22

Friday, Jun 06, 2008 at 06:22
Mr Troopy, I like your philosophy but unfortunately I'm not driving a GTHO. When I put my foot down detuned 200hp 351 attempts to propel 3 tonne F100 with limited succcess. Must be a better way. Still thinking of juicing Elle though (showing your age mate)
AnswerID: 308045

Reply By: Hairs (NSW) - Friday, Jun 06, 2008 at 07:00

Friday, Jun 06, 2008 at 07:00
That's not good at all. I'd rather have a Dinosaur that plastic. I've owned many 302's & 351's in sedans and wagons over the years. With both manuals and automatics run gears from 4.11 to 2.75 in LSD Nine Inches. From XW to XC's. I even had one with a Holley 750 double pumper on her and she never got that kinda mileage. As a young fella the peddle was always planted hard on the floor.

I'm having a guess here that it is a Stock 4 Barrel Thermaquad. Never owned one of them so I can't comment on how to tune it. Always had Holleys cause they are really easy to tune, Power valves, jets it's all relevant to your diff ratio.
If it is a Thermaquad I remember someone telling me once that the Bakelite(wrong spelling I think) base over time wears and causes leakage of both fuel and air.
If it hasn't got a Holley on her I'd put one on. I'd get a 600 Square bore. That should do the trick just nicely.
I'd also chase up your local street machine club and track down someone that is a Ford Nut through and through. Amazing what a cartoon of beer can do.
You should be getting better mileage than that.
Others may have other ideas, but that's my Two Bobs worth.
Hope you get her sorted, they're a good old motor when running sweet.

AnswerID: 308046

Follow Up By: MrBitchi (QLD) - Friday, Jun 06, 2008 at 07:25

Friday, Jun 06, 2008 at 07:25
Have to agree with the Holley answer. Used to run a 650 double pumper on my HQ 308. Went like stink and was real easy to tune. Had the same setup on our Ski Boat and used to get good fuel economy out of that as well. It was a club boat so economy was important..

Stick with the smallest 4barrell job you can get. Don't fall for the "bigger is better" line. That really only applies to the drag strip.
FollowupID: 573867

Follow Up By: MrBitchi (QLD) - Friday, Jun 06, 2008 at 07:52

Friday, Jun 06, 2008 at 07:52
Maybe you're running a 2 barrel already? Same principal applies. About a 400 2 barrel would be good.
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Follow Up By: DCTriton - Friday, Jun 06, 2008 at 09:55

Friday, Jun 06, 2008 at 09:55
I think you may be right Mrbitchi - an old fairlane I had was a 351 with spaghetti manifold and 350 holley, it was thirsty and lame... I got a 500 holley 2barrel from a mate which made a difference but the torquer manifold and 600 4 barrel made the biggest difference, better fuel economy with 'normal' driving but had the balls to overtake when required... You can also get a 465 4 barrel which may be all you need - jeez, this could go on for ever...
FollowupID: 573897

Follow Up By: G.T. - Monday, Jun 09, 2008 at 12:34

Monday, Jun 09, 2008 at 12:34
HAIRS --- Saw BIG302 in town (Gold Coast ) yesterday (Sunday 8th) Standout vehicle , this is why I noticed it. Regards G.T.
FollowupID: 574763

Follow Up By: Hairs (NSW) - Monday, Jun 09, 2008 at 17:07

Monday, Jun 09, 2008 at 17:07
Cheers G.T.
Good to hear she is still alive. Ya can't kill'em with a big stick.
It brings back some very good memories.

Thanks, ;-)
FollowupID: 574814

Reply By: stevesub - Friday, Jun 06, 2008 at 07:08

Friday, Jun 06, 2008 at 07:08
Rather than spending money to make your current vehicle more economical - (and that will be hard to do without a new hi-tech petrol or diesel motor) why not keep the dinosaur and use the money to buy a small economical car and use that for the times when you can get away with it.

Even with a new hi tech motor, look and see what the latest ones get for fuel consumption. They are not that good but better than what you are getting.

There is at the end of the day not a lot you can do to improve what you already have. Some minor improvement may happen with a decent tune-up, hi flow air cleaner, maybe re-jetting of the carb, correct tyre pressures and most of all a very light right foot and anticipation of the red lights, corners or anywhere you have to slow down. Use the brakes and gears as little as possible to slow down, just lift the right foot earlier. A 3 ton+ truck will go along way on momentum alone - we know, we run a Rangie and Troopy.

Think before you buy, if you spend $10,000 to make your truck more fuel efficient, that is a lot of fuel, even at today's prices.

Even if you cannot go the car route, it may be time to flick the old girl off and get a newer more fuel efficient model.

AnswerID: 308048

Reply By: landed eagle - Friday, Jun 06, 2008 at 07:32

Friday, Jun 06, 2008 at 07:32
In another life I had a 302 XB GS Panel van. Usually crammed full of music gear (not light stuff). Ran the thing on a 350 holley carby and it was brilliant! No good for boy racer stuff, but great for long trips to gigs from one end of tassie to the other.When it was empty it would travel as well as any of my mates vehicles on open road. And they were running big double pumpers.
Wish I still had it,was most reliable vehicle I've ever owned.Now tow caravan with a 94 EF 4.0 litre. Travelling at 90km/h saves heaps of fuel.
AnswerID: 308052

Reply By: Member - Toolman (VIC) - Friday, Jun 06, 2008 at 08:20

Friday, Jun 06, 2008 at 08:20
I had a Bronco with the same motor and with a 4 barrel holley downdraft carbi in it. I achieved very similar fuel consumption to you. I solved the problem by selling it and getting a diesel landcruiser.

Since then I have been wondering if it would have been viable to put a diesel motor in it? But that's in hind sight. It was a most capable tow vehicle as far as grunt was concerned.

AnswerID: 308057

Reply By: Member - Matthew C - Friday, Jun 06, 2008 at 10:15

Friday, Jun 06, 2008 at 10:15
Ok thats not so good.

My GQ patrol powered by Vortec 350 gets 340 k's out of 88 litres of gas around town and towing fully loaded only about 250 so its about the same as you .

Your figures are not towing though are they.

AnswerID: 308092

Reply By: Best Off Road - Friday, Jun 06, 2008 at 10:45

Friday, Jun 06, 2008 at 10:45
That's around 8.5 mpg.

I had an XC 302 years ago and I used to get about 13 mpg. Given your is a 351, F100 is bigger and heavier, LPG increases comsumption by 20% or more it's about all I would expect.

Given that LPG is about one third the cost of diesel you're doing well. Try to find a diesel vehicle of the size you've got and with the grunt you've got that will return 25 mpg. It'll be parked in the same street that the Easter Bunny lives in.


AnswerID: 308099

Follow Up By: Hairs (NSW) - Friday, Jun 06, 2008 at 17:53

Friday, Jun 06, 2008 at 17:53
Now your bringing back some memories.
She even had the number plate 'BIG 302"
FollowupID: 573978

Follow Up By: Hairs (NSW) - Friday, Jun 06, 2008 at 17:56

Friday, Jun 06, 2008 at 17:56
Sorry tried to insert a photo.
Didn't work.
Here,s the link
FollowupID: 573979

Reply By: Member - Shane D (QLD) - Friday, Jun 06, 2008 at 17:51

Friday, Jun 06, 2008 at 17:51
My mate turfed his 351EFI and fitted a 5.9 litre 6cyl Cummins (ex dodge ram) into his effie.
Pretty big job, imported himself from the states/Canada, fitted himself good for 250hp/500ft pd torque, and claims to be getting high 20's /30's MPG.
Took him 2 months to get it right, stuff like vacuum for brakes, bell housings to suit his 5 speed manual, fuel lines mounting and wiring the new ECU (electronic motor),fitting a long 6 into a space a V8 meant to relocate the radiator, as well as mounting an intercooler, BIG job, but he reckons now it's worth it, trying to get me to drop one into my 100 series!
The whole exercise set him back around $10k

AnswerID: 308171

Reply By: moose351 - Tuesday, Jun 10, 2008 at 22:54

Tuesday, Jun 10, 2008 at 22:54
Hi 351c.
I have an 85 Effie trayback with 351clevo. running dual fuel and averaging 3.5 ish km/litre overall - about 30,000km since restoration and recon engine. Mostly gas these days but some petrol out bush. only using about 10% more gas than petrol. I doubt theres much you can do. ive tried lots of tuning options. find someone who knows how to tune carbys. be careful with holleys on steep downhills, they flood badly!! most of my driving is on trips loaded to the gunnels. i bought a truck avenger carby that was supposed to fix flooding. had lots of probs with flatspots. its a 670cfm 4 barrel square bore on an aluminiun torqer? manifold. plenty of power and 25 - 30 l/100 is ok for what it is - a besser block on wheels. im happy with mine. cant justify spending 30ish grand on a flashy tojo or datto. i love my effie!


AnswerID: 309136

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